1. Field of the Disclosure
The disclosure relates to optoelectronic devices.
2. Brief Description of Related Technology
Current imaging systems require heavy and expensive compound lenses to project an object onto a flat focal plane array. Modern camera systems employ multiple, high f/number lens elements to create a distortion-free image on a flat focal or film plane.
In contrast, biological systems employ a hemispherical image plane, thereby simplifying the imaging optics. The approximately spherical human eye provides a nearly ideal imaging system. It is both compact and simple, with a wide field of view free of image distortion and a low f/number.
Creating an imaging system that mimics the form and function of the eye involves fabricating a focal plane onto a nearly spherical surface that matches the curvature of a single lens element. Fabrication of such focal planes presents the challenge of creating a high density of monolithically integrated photodetectors on a three-dimensionally curved surface.
One approach to fabricating photodetectors on curved surfaces uses an organic focal plane array (FPA) and a preformed plastic hemisphere. See Xu et al., “Direct transfer patterning on three-dimensionally deformed surfaces at micrometer resolutions and its application to hemispherical focal point detector arrays,” Organic Electronics, vol. 9, pp. 1122-1127 (2008). The organic FPA in Xu includes organic double heterojunction photodetector structures having a copper phthalocyanine (CuPc) donor layer, a C60 acceptor layer, and a bathocuproine (BCP) exciton blocking layer. These organic materials are well suited for deposition onto a hemispherical substrate, but unfortunately present other fabrication challenges and performance limitations.